The invention relates to a radiation device for radiation therapy, and more particularly, a rapid exchange radiation device which is used in a percutaneous transluminal coronary angioplasty (PTCA) procedure and/or in a stent implantation into a patient's body lumen.
The PTCA procedure has been a standard procedure for re-vascularization of coronary artery. For example, in the PTCA procedure, a catheter having a balloon at the distal end is introduced into the coronary artery to enlarge a stenosis, i.e. constriction in the coronary artery. However, re-stenosis and re-closure of the lesion after the PTCA procedure is a problem thereafter. Namely, in 35 to 40 percent of the angioplasty cases, re-stenosis occurs within 6 months after the PTCA procedure.
In the treatment of the stenosis in the artery, there has been used another device called "stent", i.e. generally tubular shaped device which functions to support a desired part of the artery, such as a lesion enlarged by a balloon catheter, from the inside thereof. The stent prevents occurrence of re-stenosis, and lowers the rate of re-stenosis to 13 to 19%. Furthermore, according to the recent study, radiation therapy combined with a stent implantation has shown better results, and lowers the rate of occurrence of re-stenosis to 1 to 9%. Therefore, it is better to use radiation therapy combined with the stent implantation in the PTCA procedure for preventing re-stenosis.
Radiation therapy as stated above can be used in the standard PTCA procedure alone as well as in the PTCA procedure combined with the stent implantation. In either case, the lesion is exposed to the pre-calculated dosage of radiation. It is believed that the exposure to radiation would partially destroy DNA of target cells damaged by the PTCA procedure or stent procedure, so that the excessive proliferation of the cells damaged by the PTCA procedure or stent procedure can be minimized.
There are several methods of applying radiation to the target cells or lesion. In the first method, a guide wire generally used in the PTCA procedure is provided with a radioactive core imbedded at the tip thereof, and radiation is applied by the radioactive core in the guide wire. In the second method, radioactive pellets or cells are mechanically located to the lesion site, and radiation is applied by the radioactive pellets or cells. After desired exposure of radiation to the lesion, the radioactive pellets or cells are removed from the lesion by the mechanical system. In the third method, radioactive fluid is injected into a PTCA balloon catheter which is frequently used in the PTCA procedure, so as to apply radiation to the target lesion.
In the above described methods, however, there are following disadvantages. Firstly, since the radioactive pellets or the device having the radioactive source, such as the guide wire having the radioactive source at the tip thereof, are placed directly inside a patient's body lumen, such as an artery, the radioactive pellets or the device with the radioactive source are not used again.
Also, in the method using the guide wire with the radioactive source at the tip thereof, in order to apply radiation therapy, the guide wire preliminary inserted inside the patient's lumen for another treatment in the PTCA procedure has to be withdrawn first, and the guide wire having the radioactive core has to be introduced inside the patient's body lumen again to locate the tip of the guide wire at the lesion. Thus, exchange of the guide wire in the meandering body lumen is cumbersome and may cause damage to the artery or blood vessel.
Furthermore, after enough dosage of radiation is applied to the lesion, the radiation catheter is required to be withdrawn as quickly as possible so as not to cause excessive radiation. Also, it is required that the radiation device should be handled quickly because of its affect to other people. Thus, it has been sought that the radiation therapy can be made easily and quickly.
Accordingly, an object of the invention is to provide a radiation device, which can provide radiation only to a required portion in a body lumen at a required time.
Another object of the invention is to provide a radiation device as stated above, wherein a radiation source can be placed inside the body lumen smoothly and rapidly, and can be removed quickly from the required portion after enough dosage of radiation.
A further object of the invention is to provide a radiation device as stated above, wherein the radiation source once used inside the patient's body lumen can be reused.
A still further object of the invention is to provide a radiation device as stated above, wherein the radiation source can be introduced into the required portion by a guide wire used in the general PTCA procedure.
Further objects and advantages of the invention will be apparent from the following description of the invention.